Light‐Emitting Diodes

Abstract Light‐emitting diodes ( LEDs ) are the most common light source. They are used in a myriad of applications including general lighting and back‐lighting for displays. LEDs are based on pn junctions, usually made of III ‐ V semiconductors, which emit light when a forward current is injected. This chapter discusses the fundamental properties and performance metrics of LEDs . Particular attention is given to the efficiency of LEDs and the various mechanisms that reduce the efficiency. The chapter also discusses white LEDs that consist of a blue LED chip that is coated with a yellow phosphor. The phosphor absorbs some of the blue light and converts it to broadband yellow light. White LEDs are very suitable replacement light sources for conventional sources such as incandescent and fluorescent lamps.